• Updated 2023-07-12: Hello, Guest! Welcome back, and be sure to check out this follow-up post about our outage a week or so ago.

Macintosh PLUS mystery ticking / clicking when floppy in drive


my old Mac Plus is wierd.
I replaced all capacitors and U3 with a 4N35 chip . CR1 and CR5 too. It starts with a floppy disk symbol and start sound. But when I insert a floppy disk it makes clicking noises on the analog board and immediately ejects the floppy disk, then the clicking stops. I measured 5.09 volts at the mouse connection.
I also tried another drive but it does the same thing.


Well-known member
My Plus makes a faint clicking sound roughly every 1 second when there's no disk inserted. I'm pretty sure it's from the Mac repeatedly checking for a disk, but I don't know why that involves an audible sound. What disk are you testing with? Have you tried it in another computer to verify it's good?

Have you measured the 12V supply?


Well-known member
That's a little bit off, but probably fine. 12V is used to power the drive motors, and not for any digital circuitry, so the voltage doesn't need to be exact. Can you tell us more about the clicking noises? Have you verified that the disk you're using is a good one?